Polyurethane resin which can provide films and molded articles having abrasion resistance, adhesive properties, nonviscous properties and rubber elasticity or the like, is widely used as a coating material, an adhesive agent, a binder and a coating agent or the like.
In conventional solvent type coating materials, high flammability and odor or the like are unavoidable while at work. Therefore, various improvements such as an improvement of the environment, an advancement of working efficiency and reducing industrial wastes like solvent wastes are required, and aqueous coated materials are expected to be promising from safety standpoints such as prevention of environmental contamination and better labor hygiene.
For example, polyester fibers or nylon fibers have been used for curing net, mesh and sheet which are used at building sites. These polyester fibers and nylon fibers are usually coated with polyvinyl chloride sol in order to impart flame retardancy, waterproof properties, weather resistance and durability to them. Furthermore, plasticizers such as DOP (dioctyl phthalate) could be added to this polyvinyl chloride sol.
However, with concerns about the environment, the request that the above polyvinyl chloride sol should be replaced with other materials has become stronger due to the problem of poisonous gas such as dioxine produced when these curing net, mesh and sheet are burned and the problem that plasticizers such as DOP are environmental hormones.
In addition, although polyvinyl chloride in itself has a certain degree of flame retardancy, it is often the case that a flame retardant is further added. Generally, it is often the case as well that this flame retardant is a compound containing halogens such as bromine and chlorine, thereby poisonous gases such as dioxin are produced, which is a problem. In order to solve these problems, polyphosphate, phosphorous compounds such as aromatic condensed phosphoric acid ester and also an inorganic compound such as magnesium hydroxide are used as disclosed in the following patent documents 1 to 3. However, since the above addition type phosphorous compound has a plasticizing effect as well, when it is added in large amounts, the strength of coating film extremely drops, and also tackiness and bleed phenomenon of the surface of coating film occur, which are problems. In addition, there are problems that as long as a large amount of inorganic flame retardant is not added the coating film cannot have the effect of flame retardancy, and moreover the performances of the coating film such as abrasion resistance and plasticity become poor. In either case, satisfactory coated articles have never been obtained.